The COMP3 command contains 4 fields for configuring the control loop.

The EN_SS_DCM bit sets the operation mode during the soft-start ramp. With value "1" on this bit, the device is forced to under DCM operation during the soft-start ramp. This bit doesn't control the operation mode after the soft-start ramp completes.

The SEL_NOC_TON bit selects the on-time reference for a NOC operation and thus determines the high-side FET conduction time during a NOC operation period. The on-time option selected here can help to avoid two undesired behaviors:

• For relatively low VOUT applications (such as VOUT = 1.1 V) using longer t_{ON_NOC} helps to prevent negative current run-away behavior. A NOC run-away behavior occurs when the inductor current moves more negatively during low-side FET conduction time than the movement during high-side conduction time. A NOC run-away behavior can lead to excessive stress on low-side FET and raise the concern of FET reliability.
• For applications with an extra large inductor current ripple (≥ 10 A) and the NOC threshold is set to a less negative value (for example NOC threshold = −7.5 A), the average current during the NOC operation is likely not that negative. This leads to insufficient discharge on VOUT and thus the load is stressed under the overvoltage condition for a longer period. To build sufficient negative current during the NOC operation, select the shorter t_{ON_NOC} to reduce the positive inductor current movement during the high-side on-time. A design example of this kind of case is VCCFA_EHV rail which can have the following configuration: PVIN = 12 V, VOUT = 1.8 V, f_SW = 1 MHz, L_OUT = 150 nH, ICC_MAX = 10 A, and NOC threshold = −7.5 A. To have sufficient discharge on VOUT, the design can either select the shorter t_{ON_NOC} or set ICC_MAX to 15 A so that the NOC threshold is more negative (such as −15 A).

These SEL_LO_CS bits select the L_OUT (output inductor value) for the current sensing circuit. The TPS544C26 IC utilizes the output inductor value entered here to build an accurate output from the current sense circuit. Please choose a value closest to the inductor that is used in a BOM. For any inductor value higher than 400 nH, set SEL_LO_CS to 11b. Selecting a value that is significantly different from the real inductor (for example, 400 nH used but 100 nH selected) can lead to an inaccurate current sense output which can cause unexpected control loop behavior and also an inaccurate READ_IOUT telemetry report.

The DCLL bits determine the DC load line setting. Select a DCLL value per the requirement from the processor or the load, otherwise, the load regulation can be out of expectation.

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